<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>边框</title>
  <style>
    .box {
      width: 300px;
      height: 300px;
      background-color: red;

      /* 内缩 */
      box-sizing: border-box;

      /* 
      边框 
      线条样式: solid(实线) dashed(虚线) double(双线)
      */
      /* border: 10px solid #000; */
      border-left: 10px solid green;
      border-right: 10px solid orange;
      border-top: 10px solid pink;
      border-bottom: 10px solid skyblue;
    }
  </style>
</head>

<body>
  <div class="box">我是div标签</div>
</body>

</html>